JPH04215681A - Transfer device - Google Patents

Abstract

PURPOSE:To prevent a transfer blur and a transfer omission by improving the adhesion between a photosensitive belt and a transfer roller across the transfer paper. CONSTITUTION:The carrier of a photosensitive belt 1 is formed with a nickel seamless belt made of a magnetic substance, a transfer roller 12 is formed with a nonmagnetic conducting sleeve 21 provided with a polyurethane thin layer on aluminum storing a fixed magnet 22, and the photosensitive belt 1 and the transfer roller 12 are closely stuck by the mechanical pressing force and the magnetic attracting force.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a transfer device employed in an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a printer. The present invention relates to a transfer device that transfers images onto a transfer material using a transferred roller.

0002

[Prior Art] Methods for transferring a toner image formed on a latent image carrier to a transfer material such as transfer paper include a corona transfer method and a roll transfer method using a transfer roller imprinted with a bias for forming a transfer electric field. The law is well known. In the corona transfer method, a high voltage is applied to a conductive wire to generate a discharge, and the charge due to corona ions generated by this discharge is accumulated on the transfer paper, and the Coulomb force exerted on the toner on the image carrier causes the charge to be transferred. This method transfers the toner to a transfer paper, but it has problems such as deterioration of image bearing members such as photoreceptors due to ozone generated during discharge. On the other hand, in the roller transfer method, an electric field is formed by the transfer roller, so there is no such problem. When using a drum-shaped photoreceptor, this transfer roller has a width (hereinafter referred to as
In order to obtain a nip width (referred to as nip width), the nip width is generally made of an elastic member. However, in this method, because the diameter of the elastic roller changes at the nip, a slight linear speed difference occurs between the transfer paper and the photoreceptor drum.
Transfer misalignment will occur. For this reason, various measures are often taken before entering the transfer area.

On the other hand, when the photoreceptor is in the form of a flexible belt, the transfer roller does not need to be made of an elastic material as described above, and the slack of the belt can be utilized by using a highly hard roller. Since the specified nip width can be obtained by
There is no need to worry about the linear velocity deviation as described above. However, in terms of uniform adhesion, when a flexible belt is used, slight distortion during conveyance of the belt may partially deteriorate the adhesion with the transfer roller, affecting transfer performance. .

[0004] It is known that magnetic toner on a drum-shaped photoreceptor is transferred to a transfer material using a magnetic roll to which a transfer bias is applied (for example, JP-A-55
-100581), which mainly uses a magnetic roll to transfer magnetic toner using magnetic force, and uses a transfer roller that forms an electric field to transfer the toner on a belt-shaped photoreceptor. No suggestion has been made to improve the adhesion between the toner on the photoreceptor and the transfer material when the toner is transferred onto the transfer material.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and its object is to transfer a toner image on a belt-like image carrier. An object of the present invention is to improve the adhesion between a transfer material and an image carrier in a transfer device that transfers images onto a transfer material using a roller.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for carrying out toner images on a belt-like image bearing member.
A transfer device that transfers images onto a transfer material using a transfer roller is characterized in that the support of the image carrier is made of a magnetic material, and the transfer roller is provided with a magnetic field generating function. A high resistance protective layer may be provided on the surface of this transfer roller. Further, as this transfer roller, for example, a finely magnetized magnet roller can be used.

[0007]

[Operation] Due to the magnetic field generation function of the transfer roller, the support of the image carrier made of a magnetic material is attracted to the transfer roller by magnetic force, and as a result, the transfer roller, image carrier, and transfer material are brought into close contact with each other. Adhesion between the surface of the image carrier and the transfer material is improved. Furthermore, if a high-resistance protective layer is provided on the surface of the transfer roller, even though a relatively high voltage is applied between the support of the image carrier and the transfer roller to form a transfer electric field, Even if there are undesirable protrusions on the surface of the image carrier or the transfer roller, it is possible to prevent concentrated discharge from occurring there. Furthermore, when using a finely magnetized magnetic roller as a transfer roller, if magnetic powder is mixed with rubber or plastic and formed on the roller, and this roller is finely magnetized, it can be equipped with a magnetic field generation function. A transfer roller with a simple structure can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a transfer device of an electrophotographic printer, which is an image forming apparatus, will be described. FIG. 1 is a front view showing the configuration of main parts of an electrophotographic printer according to this embodiment. In FIG. 1, a photoreceptor belt 1, which is an image carrier, is supported by support rollers 2, 3, and 4, and is driven so that its surface moves in the clockwise direction of the arrow. This photoreceptor belt 1 has a thickness of 30 μm and a circumferential length equivalent to a circumferential length of 60 mm in diameter, and is formed by a subbing layer, a charge generation layer, and a charge transfer layer on top of a nickel seamless belt made by electroforming. This is an OPC photoreceptor belt constructed by sequentially laminating layers. This photoreceptor belt 1 is uniformly charged by a charger 5. As the charger 5, a corona charger is used, but instead of this, for example, a charger that generates less ozone and has good contact may be used. Charged photoreceptor belt 1
The surface is imagewise exposed to light 6 from a laser diode (not shown) modulated by an image signal to form a latent image. The latent image on the photoreceptor belt 1 is developed with monocomponent toner on a developing roller 8 of a developing device 7. The one-component toner on the developing roller 8 is charged by agitation by the agitator 9 in the developing device and friction between the toner replenishing roller 10 and the developing roller 8, and is turned into a thin layer by the blade 11 that presses against the developing roller 8. has been done. Instead of such a developing device using one-component toner, a developing device using two-component developer, a one-component magnetic brush developing device,
A jumping developing device or the like may also be used. The toner that adheres to the photoreceptor belt 1 during development is removed from the photoreceptor belt 1.
At the contact portion between the transfer roller 12 and the transfer roller 12, the image is transferred to a transfer paper, which is a transfer material, which has entered the transfer guide plate 13 and the like. Thereafter, the paper is separated by the curvature of the support roller 3, and is discharged outside the machine through a fixing device (not shown). After the transfer, residual toner is removed from the surface of the photoreceptor belt 1 by the cleaning blade 15 of the cleaning device 14, and the surface is then prepared for charging.

Next, the transfer roller 12 will be explained in detail. The transfer roller of this example, as shown in FIG. 2(b),
A non-magnetic conductive sleeve 21 that is pressed against the surface of the photoreceptor belt 1 to form a predetermined transfer nip, and to which a bias is applied by a power source 20 to form a transfer electric field.
and a fixed magnet 22 disposed inside the non-magnetic conductive sleeve so as to face the transfer nip side. This non-magnetic conductive sleeve 21 is made of aluminum, for example, and has a thin layer of polyurethane formed on the sleeve surface. This thin layer of polyurethane is used to prevent abnormal discharge due to protrusions on the aluminum surface and to prevent slipping between the transfer paper and the transfer roller 12. Therefore, any material with dielectric strength, medium to high resistance, and a large coefficient of friction can be used in place of the polyurethane thin layer. Further, if there is no risk of abnormal discharge or slipping, a material with poor dielectric strength or a relatively small coefficient of friction may be used, and furthermore, such a surface layer may be omitted. The non-magnetic conductive sleeve may be rotated by frictional force from the surface side of the photoreceptor belt 1, or may be driven by a drive mechanism such that it moves in the same direction at the contact portion with the photoreceptor belt 1. It may be driven.

In the above configuration, the transfer nip includes not only the pressure force of the transfer roller against the surface of the photoreceptor, but also the attraction between the nickel belt, which is a support for the photoreceptor belt made of a magnetic material, and the fixed magnet 22 of the transfer roller 12. A force acts, which causes
The surface of the photoreceptor belt and the surface of the transfer roller come into close contact with the transfer paper sandwiched between them, and as a result, a transfer electric field is applied while the toner on the surface of the photoreceptor belt 1 is in close contact with the transfer paper, so that good transfer is performed.

As the transfer roller 12, this fixed magnet 2
2 (instead of the non-magnetic conductive sleeve 21 with built-in
It is also possible to use the rollers shown in a) or (c) of the same figure. The roller 30 shown in FIG. 2(a) is made of rubber or resin made by adding magnetic fine powder such as ferrite to ethylene propylene rubber (EPDM) or nylon resin. This is a magnet roller that is finely magnetized. Even when this magnet roller 30 is used, the magnetic support of the photoreceptor belt 1 and the magnet roller 30 are attracted to each other by magnetic attractive force, and it is possible to achieve close contact between the two with the transfer paper sandwiched therebetween. The roller 40 shown in FIG. 2(c) is
This is a magnetic roller with a protective layer, in which a protective layer 41 having a resistance greater than that of the magnetic roller 30 is provided on the surface of the magnetic roller 30 shown in a). This is because the transfer roller in Fig. 2(a) is not conductive but has medium resistance, and the magnetic fine powder may be unevenly dispersed. This prevents uneven transfer, etc., from occurring due to variations in electrical characteristics.

0012

According to the present invention, the adhesion between the surface of the image carrier and the transfer material is improved, and a uniform pressure contact state can be maintained.
It has the excellent effect of being able to obtain a good transferred image without transfer blur or transfer omission. Furthermore, if a high-resistance protective layer is provided on the surface of the transfer roller, even though a relatively high voltage is applied between the support of the image carrier and the transfer roller to form a transfer electric field, Even if there are undesirable protrusions on the surface of the image carrier or the transfer roller, no concentrated discharge occurs there. Further, even in particularly high temperature and high humidity environments, no local unequal electric fields occur, and stable transfer performance can be obtained. Furthermore, when a finely magnetized magnetic roller is used as the transfer roller, the mechanical structure of the transfer roller is simple, and a highly reliable transfer device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a schematic configuration of an electrophotographic printer according to an embodiment.

2 shows rollers that can be used as the transfer roller 12 in FIG. 1, in which (a) is a magnetic roller, (b) is a roller with a fixed magnet arranged in a non-magnetic sleeve, and (c) is ( This figure shows a roller in which a relatively high-resistance surface layer is provided on the surface of the magnet roller of a).

[Explanation of symbols]

1 Photoreceptor belt 7 Developing device 12 Transfer roller 20 Power supply 21 Non-magnetic conductive sleeve 22 Fixed magnet 30 Magnet roller 40 Magnet roller with protective layer 41 Protective layer

Claims (3)

[Claims] 1. A transfer device that transfers a toner image on a belt-shaped image carrier to a transfer material using a transfer roller, in which a support of the image carrier is made of a magnetic material, and a magnetic field is applied to the transfer roller. A transcription device characterized by having a generation function. 2. The transfer device according to claim 1, wherein a high resistance protective layer is provided on the surface of the transfer roller. 3. The transfer device according to claim 1, wherein the transfer roller is a finely magnetized magnet roller.